Connexion a une base de données avec PHP PDO

<?php

header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Credentials: true ");
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS');
header("Access-Control-Allow-Headers: X-Custom-Header, Origin, Content-Type , Authorisation , X-Requested-With");
header("Content-Type: application/json; charset=UTF-8 ");


$json = file_get_contents('php://input');
$decoded = json_decode($json);

$email = htmlspecialchars($decoded->email, ENT_QUOTES);
$pass = htmlspecialchars($decoded->password, ENT_QUOTES);

function conn ()
{
	$dbhost="localhost";
	$user='smartlibffsmart';
	$pass='smartlibffsmart';
	$db='smart';

	$conn = new PDO('mysql:host=smartlibffsmart.mysql.db;dbname=smartlibffsmart', $user, $pass);
	return $conn;
}

function encrypt_decrypt($action, $string)
{
	$output = false;
	$encrypt_method = "AES-256-CBC";
	$secret_key = 'WS-SERVICE-KEY';
	$secret_iv = 'WS-SERVICE-VALUE';
	$key = hash('sha256', $secret_key);
	$iv = substr(hash('sha256', $secret_iv), 0, 16);
	if ($action == 'encrypt') {
		$output = base64_encode(openssl_encrypt($string, $encrypt_method, $key, 0, $iv));
	} else {
		if ($action == 'decrypt') {
			$output = openssl_decrypt(base64_decode($string), $encrypt_method, $key, 0, $iv);
		}
	}
	return $output;
}

if (empty($email) || empty($pass) || mb_strlen($pass) < 6 || mb_strlen($pass) > 30 ){
json_encode(false);
	die;
}else{

$db = conn();
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$password = encrypt_decrypt('encrypt',$pass);

$res = $db->prepare("SELECT * FROM user WHERE email = ? and password = ? ");
$res->execute([$email,$password]);
$values = $res->fetchAll();

echo json_encode(sizeof($values) > 0 ? true : false);
}

?>